const { Machine } = XState;

/**
 * The state machine that will power our payment form.
 *
 * This machine can be visualized copying the object we
 * pass to `Machine()` through xviz
 *
 * @see  https://bit.ly/xstate-viz
 */
const stateMachine = Machine({
  initial: "idle",
  states: {
    idle: {
      on: {
        SUBMIT: [
          {
            target: "loading",
            cond: ({ state }) => state.name !== "" && state.card !== ""
          },
          { target: "error" }
        ]
      }
    },
    loading: {
      onEntry: ["doPayment"],
      on: {
        PAYMENT_RECEIVED: "success",
        PAYMENT_FAILED: "error"
      }
    },
    error: {
      on: {
        SUBMIT: {
          target: "loading",
          cond: ({ state }) => state.name !== "" && state.card !== ""
        }
      }
    },
    success: {
      on: {
        RESET: "idle"
      }
    }
  }
});

/**
 * We don't actually have a backend service for this
 * payment system. So, instead we're rolling a Math.random
 * dice and resolving or rejecting a fake payment promise.
 */
function fakePayment() {
  return new Promise((resolve, reject) => {
    setTimeout(() => {
      const dice = Math.floor(Math.random() * Math.floor(2));

      if (dice === 0) return resolve("Payment succeeded.");

      return reject("Payment failed.");
    }, 1000);
  });
}

class App extends React.Component {
  state = {
    machine: {},
    name: "",
    card: "",
    msg: ""
  };

  // Initialize the state machine
  componentDidMount() {
    this.setState({ machine: stateMachine.initialState });
  }

  /**
   * When our machine enters the loading state, fire off
   * a call to our fakePayment() promise.
   */
  doPayment = () => {
    return fakePayment()
      .then(msg => this.transition("PAYMENT_RECEIVED", { msg }))
      .catch(msg => this.transition("PAYMENT_FAILED", { msg }));
  };

  /**
   * We need a way to call the function we define as a string
   * in our onEntry action in the loading state.
   *
   * If you're going to leverage any of the other action types,
   * check out what Michele Bertoli has done in react-automata.
   *
   * @see https://github.com/MicheleBertoli/react-automata/blob/master/src/withStateMachine.js#L79
   */
  runActions = state => {
    if (state.actions.length > 0) {
      state.actions.forEach(f => this[f]());
    }
  };

  // Transition based on current state and extState
  transition = (eventType, extState) => {
    // Determine the next state
    const newState = stateMachine.transition(
      this.state.machine.value,
      eventType,
      {
        state: this.state
      }
    );

    // Perform any actions for the new state
    this.runActions(newState);

    // Update our component state
    this.setState({
      machine: newState,
      msg: extState && extState.msg ? extState.msg : ""
    });
  };

  // Prevent the form from refreshing the page
  submitForm = e => {
    e.preventDefault();
    this.transition("SUBMIT");
  };

  handleInput = e => {
    this.setState({ [e.target.name]: e.target.value });
  };

  render() {
    const { machine, msg } = this.state;

    return (
      <div>
        <div className="pill-container">
          <div className="state-pill">current state: {machine.value}</div>
        </div>

        <div className="form-container">
          <div className="form-header">
            <h2>State Machine Payment Form</h2>
          </div>

          {machine.value === "error" ? (
            <div className="alert error">
              {msg ? msg : "You must fill out all the form fields."}
            </div>
          ) : null}

          {machine.value === "success" ? (
            <div className="alert success">{msg ? msg : null}</div>
          ) : null}

          <div className="form-body">
            <form onSubmit={e => this.submitForm(e)}>
              <div className="form-group">
                <label htmlFor="NameOnCard">Name on card</label>
                <input
                  id="NameOnCard"
                  name="name"
                  className="form-control"
                  type="text"
                  maxlength="255"
                  value={this.state.name}
                  onChange={this.handleInput}
                />
              </div>
              <div className="form-group">
                <label htmlFor="CreditCardNumber">Card number</label>
                <input
                  id="CreditCardNumber"
                  name="card"
                  className="null card-image form-control"
                  type="text"
                  value={this.state.card}
                  onChange={this.handleInput}
                />
              </div>
              <button id="PayButton" className="btn-success" type="submit">
                Pay Now
              </button>
            </form>
          </div>
        </div>

        {machine.value === "success" ? (
          <button
            id="ResetButton"
            className="btn-reset"
            type="button"
            onClick={() => this.transition("RESET")}
          >
            Reset
          </button>
        ) : null}
      </div>
    );
  }
}

ReactDOM.render(<App />, document.getElementById("app"));